Currently, approximately 7 million Americans use hearing aid devices, which usually use compact Zn-air batteries. These batteries are relatively inexpensive, safe to use, and easy to dispose of, but only work for approximately 1 week before needing to be replaced. Practically all other modern gadgets (cell phones, computers, etc.) now utilize rechargeable lithium-ion (Li-ion) batteries, which have lower charge capacity and need frequent (practically daily) recharging. Although frequent recharging may be acceptable for gadget users, it may create potentially a life threating situation for users of medical devices. Th frequent need to replace or recharge hearing aid batteries creates a logistical problem for users, especially for seniors, who constitute the largest segment of hearing aid users. In response to the NIH National Institute on Deafness and Other Communication Disorders (NIDCD) request for new rechargeable batteries for hearing aid devices, Physical Optics Corporation (POC) proposes to develop a new High-Capacity Li-ion Rechargeable (HCLIR) battery. The significant (fourfold) increase in the battery capacity, compare to the current capacity of Li-ion batteries wil be achieved with a new silicon (Si) microporous anode. Si has an outstanding lithium (Li) insertion capacity, which is 10 times higher than conventional graphite, but suffers from large volume changes while absorbing and releasing Li. The proposed anode structure not only significantly increases surface area available for the reaction with Li, but also permits material extension, thus allowing for multiple charge/discharge cycles. As a result of this innovation, the proposed compact battery (size A312) will be capable of storing energy sufficient for approximately 1 week of hearing aid operation without recharging. Users will be able to recharge the battery using the same (or similar) charger they use for their cell phones and other gadgets, with an additional compartment for a small size battery. The cost of the proposed battery will be completely recovered after several months of use, while its service life will be several years long. In Phase I, POC will demonstrate the feasibility of the proposed A312 size battery with a Si microporous anode by optimizing the battery design, fabricating battery prototypes, measuring their capacity, and demonstrating their capability to withstand multiple charge/discharge cycles. In Phase II, POC will optimize the manufacturing technology to reduce battery cost. We will also certify the developed battery according to ANSI/IEC requirements. Successful accomplishment of the proposed development will directly benefit millions of hearing aid users. The proposed technology can be modified easily for use in other medical devices and for a broad commercial market for numerous electronic devices which utilize Li-ion batteries.